The broad long-term objectives of this application are to develop new interface and socket materials that overcome the detrimental effects of residual limb shape change on artificial limb users. The materials will accommodate changes in residual limb shape and reduce the occurrence of skin breakdown. The specific aims are directed at interface mechanics, materials, and tissue response. Interface stresses during ambulation as well as diurnal and long-term residual limb shape changes will be measured on individuals with below-knee amputation. Analysis will focus on assessment of changes in interface stress as well as residual limb shape over time. The interface stress and residual limb shape data will then be used to enhance an analytical model to predict interface stress changes resulting from shape fluctuations. The model and a quantitative relationship between interface stress and time-to-breakdown in skin will then be used to evaluate tissue response for existing and new treatment methods for overcoming the detrimental effects of residual limb shape change. The health relatedness of the project is to improve the health and function of persons with amputations. The development of prosthetic interface and socket materials that overcome the detrimental effects of residual limb shape change and ultimately prevent skin breakdown will help to prevent secondary disability and morbidity in the amputee population. The objectives will be addressed using a combination of experimental and analytical techniques. Experimentally, on human amputee subjects interface pressures and shear stresses as well as residual limb shape will be measured at regular intervals over a 1-year period in clinical data collection sessions using custom-designed instrumentation. Analytically, the finite element modeling method will be used to predict skin response for different treatment methods designed to overcome the detrimental effects of diurnal and long-term residual limb shape changes, including addition/removal of socks, off-the-shelf inflatable inserts, custom-designed inflatable inserts, and smart materials.